The present invention refers to a roller straightener for rolled ferrous products, the shoulders of which are characteristically openable by means of horizontal translation (relative separation of the shoulders) for the purpose of fast changing of the rolls.
As is well known to experts of the rolling sector, in general downstream of the cooling plate of a rolling system a straightener is set which has the purpose of making the rolled ferrous products perfectly rectilinear, for example, bars or other section pieces (angle bars, etc.).
Briefly, a straightener is a machine comprising a plurality of bottom rolls and a plurality of top rolls carried by holsters. Between the said rolls (which are set with their axes parallel) are fed the pieces to be straightened arriving from the rolling process.
The bottom rolls are generally the motor-driven ones, whilst the top rolls are driven in rotation by the rolled product, which is fed between the two rows of rolls.
The shell of the said bottom and top rolls is appropriately shaped (grooved), with a configuration suited to the processing of the product coming from the rolling mill.
The distance (gap) between the top rolls and the bottom rolls is adjustable so as to enable straightening of rolled products within a certain size range.
Straighteners of a known type are, for example, described and illustrated in the Italian patents Nos. 1.205.129 and 1.205.130.
An important requirement that a straightener of the above-mentioned type must satisfy is the possibility of changing the rolls in the simplest and fastest way possible when there arises the need to straighten rolled products having profiles and/or dimensions that are considerably different from the ones currently being processed.
In straighteners of a known type, such an operation requires the replacement of the entire ensemble of rolls (top and bottom) with another one having rolls with a different configuration.
The replacement of the entire set of rolls involves stoppage of the straightening machine, removal of the rolls currently in place, and installation of new sets of top and bottom rolls. However, such a solution is long, laborious and costly.
In fact, in straighteners of the known type, the supports for the bearings of the rolls are integral with the holsters of the machine, whereas the bearings proper, during the disassembly phase, remain fixed to the shafts of the rolls themselves.
Consequently, there exists the following alternative: either each roll is equipped with its own bearings, or the bearings of the rolls that are removed must be disassembled and re-assembled on the new rolls, with all the evident operating problems that derive therefrom.
The Italian patent No. 1.205.130 proposes a solution to the problem with a straightener the framework of which carries a plurality of bottom rolls and a plurality of top rolls defining a straightening path.
According to the above patent, some of the aforesaid rolls have a smaller diameter, and others have a larger diameter, in order to form two sets of rolls of different diameters, the sets being arranged one after the other. Also provided are means for moving away the said rolls of smaller diameter from the said straightening path, or inserting them in the said path according to the transverse dimensions of the section bar to be straightened.
However, also such a solution has proved very costly since, in practice, it entails two machines in line.
A further drawback of the machines of the known type is represented by the fact that the top holsters support and withstand the forces acting on all the top rolls, whilst the bottom holsters support and withstand the forces acting on all the bottom rolls. In addition, the arrangement of the top and bottom rolls is such that the forces generated by the operation of straightening the rolled products are discharged in the sense that they cause the rolls themselves to move away from one another, with the result that the structures have to support the sum of the forces acting on all the top rolls and on all the bottom rolls. This leads to the drawback of having a very extensive structure outside all the rolls, so that a very long path is created for closing the stresses.
A general purpose of the present invention is therefore that of solving, in a simple and economic way, the problem of roll change in a roller straightener for bars and/or section pieces coming from a rolling mill.
Another purpose of the invention is to create a straightener that is structured in such a manner that the forces generated by the straightening operation on the rolled products are discharged on the resistant structure so as to close, with a short path, on themselves in groups of three rolls.
The above-mentioned purposes are achieved by a straightener having the characteristics presented in the attached main claim and in the dependent claims.